f his whites should have become yellow, and his
request that his pictures might be exposed to the sun to remedy the
defect, if it occurred, are conclusive on this subject, as far as
regards the feeling of the Flemish painters: we shall presently see that
the _coolness_ of their light was an essential part of their scheme of
color.

The testing of the various processes given in these two chapters must be
a matter of time: many of them have been superseded by recent
discoveries. Copal varnish is in modern practice no inefficient
substitute for amber, and we believe that most artists will agree with
us in thinking that the vehicles now in use are sufficient for all
purposes, if used rightly. We shall, therefore, proceed in the first
place to give a rapid sketch of the entire process of the Flemish school
as it is stated by Mr. Eastlake in the 11th chapter, and then examine
the several steps of it one by one, with the view at once of marking
what seems disputable, and of deducing from what is certain some
considerations respecting the consequences of its adoption in subsequent
art.

124. The ground was with all the early masters pure _white_, plaster of
Paris, or washed chalk with size; a preparation which has been employed
without change from remote antiquity--witness the Egyptian mummy-cases.
Such a ground, becoming brittle with age, is evidently unsafe on canvas,
unless exceedingly thin; and even on panel is liable to crack and detach
itself, unless it be carefully guarded against damp. The precautions of
Van Eyck against this danger, as well as against the warping of his
panel, are remarkable instances of his regard to points apparently
trivial:--

* * *

"In large altar-pieces, necessarily composed of many pieces, it may be
often remarked that each separate plank has become slightly convex in
front: this is particularly observable in the picture of the
Transfiguration by Raphael. The heat of candles on altars is supposed to
have been the cause of this not uncommon defect; but heat, if
considerable, would rather produce the contrary appearance. It would
seem that the layer of paint, with its substratum, slightly operates to
prevent the wood from contracting or becoming concave on that side; it
might therefore be concluded that a similar protection at the back, by
equalizing the conditions, would tend to keep the wood flat. The oak
panel on which the picture by Van Eyck in the National Gallery is